Hi,
This might be just another silly question.
I got the problem after adding automation envelope, ex. panning or volume on a track.
The track then changes to grey and there isn't possible to f.ex adjust the start of the track or
adding a slight fade out in the end.
 
I'm sure there's a button somewhere that fixes this?

Have you changed the track drop down from Clip Automation back to Clip?

Hi. You did not lock the clip by any chance? (right click, and check Clip Lock) And it turning grey, could be that it is muted (select, and click "K").
All the best.